Method and apparatus for manufacturing tire with reduced radial runout

ABSTRACT

Means for measuring deviation measures a vertical deviation of a green tire from circularity while the green tire is clamped by a green tire building drum. The green tire to be formed is shaped into a complete circle according to the measured value.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and an apparatus for manufacturing atire.

2. Description of the Related Art

In a general method for manufacturing a tire, a tread ring building drumforms a tread ring, segments of a transfer which segments are arrangedalong a circumferential direction and freely reciprocated in a radialdirection hold and send the tread ring from the tread ring building drumto a green tire building drum, the green tire building drum unites thetread ring and a carcass ply and forms a green tire, and the green tireis vulcanized.

If a green tire under manufacture has RRO (radial runout, i.e. verticaldeviation from circularity), RRO still exists after the tire isvulcanized, and the product lacks uniformity wherein rigidity of thetire is uneven and reaction force upon contacting ground fluctuates dueto the deviation from circularity.

It is therefore an object of the present invention to provide a methodand an apparatus for manufacturing a tire wherein a tire of gooduniformity is manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to theaccompanying drawings, in which:

FIG. 1 is a block diagram showing a first apparatus for manufacturing atire;

FIG. 2A is a waveform chart;

FIG. 2B is a waveform chart;

FIG. 3 is a general view of the apparatus for manufacturing a tire;

FIG. 4 is a schematic side view of a principal portion of the apparatusfor manufacturing a tire;

FIG. 5 is a schematic illustration showing a stitcher wheel;

FIG. 6 is a schematic illustration showing movement of the stitcherwheel;

FIG. 7 is a schematic illustration showing a stitcher apparatus;

FIG. 8 is a schematic illustration of a tread ring forming drum;

FIG. 9 is a flowchart;

FIG. 10 is a block diagram showing a second apparatus for manufacturinga tire;

FIG. 11A is a waveform chart;

FIG. 11B is a waveform chart;

FIG. 12 is a flowchart;

FIG. 13 is a block diagram showing a third apparatus for manufacturing atire;

FIG. 14A is a waveform chart;

FIG. 14B is a waveform chart;

FIG. 15 is a flowchart;

FIG. 16 is a block diagram showing a fourth apparatus for manufacturinga tire;

FIG. 17A is a waveform chart;

FIG. 17B is a waveform chart; and

FIG. 18 is a flowchart.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be describedwith reference to the accompanying drawings.

FIG. 3 shows an apparatus for manufacturing a tire according to thepresent invention, and this apparatus for manufacturing a tire isprovided with a tread ring forming drum 3, a green tire building drum (araw tire forming drum) 4 facing the tread ring forming drum 3, and atransfer 1 applied between the tread ring forming drum 3 and the greentire building drum 4. This transfer 1 reciprocates along a rail 5 towardarrows A and B owing to a driving apparatus not shown in the attacheddrawings.

A belt, a band, and a tread material are stuck together and shaped intoa ring, and a cylindrical tread ring W (see FIG. 4) is formed. As shownin FIG. 8, the tread ring forming drum 3 possesses segments 2 arrangedalong a circumferential direction at regular intervals, and the segments2 freely reciprocate in a radial direction.

The tread ring W formed by the tread ring forming drum 3 is taken outfrom the tread ring forming drum 3 by the transfer 1, and is sent to thegreen tire building drum 4. This green tire building drum 4 unites thetread ring W and a carcass ply 50 (see FIG. 5) and forms a green tire (araw tire). In other words, the tread ring W sent to the green tirebuilding drum 4 is stuck to a surface of the carcass ply 50 by astitcher apparatus 30 shown in FIGS. 5 to 7, and a green tire is formed.

The stitcher apparatus 30 is provided with a pair of stitcher wheels (apair of stitch rollers) 31 which freely rotate and a cylinder 32 whichreciprocates the stitcher wheels 31 in directions toward and away fromthe drum 4. The stitcher wheels 31 move from a central portion of anouter circumferential face of the tread ring W toward a marginal endportion of the outer circumferential face as shown with arrows in FIG.6.

Along with rotation of the drum 4, the stitcher wheels 31 rotate ontheir axes and move from the central portion of the outercircumferential face of the tread ring W to the marginal end portion ofthe outer circumferential face, and the tread ring W is pressed (stuck)to the carcass ply 50.

The transfer 1 is, as shown in FIG. 4, provided with a circular frame 6,segments 7 arranged on the frame 6, and an expansion and contractionmechanism not shown in the attached drawings which reciprocates thesegments 7 in a radial direction. The expansion and contractionmechanism is a mechanism, for example, a cylinder mechanism, which isknown in public and conventionally used for a transfer.

The circular frame 6 is provided with a traveling object 10 travelingalong rails 5, and the traveling object 10 possesses a base plate 11 anda fixing member 12 for keeping the circular frame 6 stand on the baseplate 11.

As shown in FIG. 1, this apparatus for manufacturing a tire possessesmeans 15 for measuring deviation for a green tire which measures avertical deviation of the green tire from circularity (RRO: radialrunout) while the green tire is clamped (inflated) by the green tirebuilding drum 4 and correcting means 14 for correcting the tire to beformed into a complete circle on the basis of the measured value. Inthis case, the correcting means 14 possesses means 16 for measuringholding (grasping) pressure for measuring tread ring holding pressure ofeach segment 7 of the transfer 1, operation means 17 for comparing themeasured deviation obtained from the means 15 for measuring deviationand the measured holding pressure obtained from the means 16 formeasuring holding pressure and operating next tread ring holdingpressure of each segment 7, and controlling means 18 for arranging apressure at which each segment 7 holds the tread ring on the basis ofthe value operated by the operation means 17.

The means 16 for measuring holding pressure comprises, for example, apressure sensor (for example, a distortion gauge) attached to a face ofthe segment 7 which face faces the tread ring, and the means 15 formeasuring deviation conducts measurements using a method for testinguniformity of a tire prescribed by JASO (Japanese Automobile StandardOrganization), wherein an encoder for detecting a rotation angle inputsa distance from a laser displacement meter measured by the meter inevery 45° into a personal computer. Moreover, the controlling means 18operates the above-mentioned expansion and contraction mechanism andchanges an expanding and contracting amount of the segment 7 on thebasis of the holding pressure operated by the operation means 17.

When the green tire has a waveform (a primary waveform) of RRO as shownin FIG. 2A, the tread ring holding pressure is arranged to have awaveform (a primary waveform) as shown in FIG. 2B which corresponds tothe primary waveform of RRO of the green tire shown in FIG. 2A. This isbecause RRO of a tire to be manufactured is influenced by the tread ringholding pressure of each segment 7 of the transfer 1 and that the RRO ofthe tire to be manufactured is improved by controlling the tread ringholding pressure.

Next, using the apparatus for manufacturing a tire composed as describedabove, a tire is manufactured in a method explained below.

First, the tread ring forming drum 3 sticks a belt, a band, and a treadmaterial in a configuration of a ring and forms a cylindrical tread ringW. Next, the tread ring W is taken out by the transfer 1, and is sent tothe green tire building drum 4. At this stage, the means 16 formeasuring holding pressure measures a holding pressure at which thesegments 7 hold the tread ring, and the measured value is inputted intothe operation means 17.

The tread ring W fits on the tread ring forming drum 3 when the treadring W is formed, therefore, in taking out the tread ring W using thetransfer 1, the tread ring W is held from its outer circumferential sideby the segments 7 of the transfer 1 and a diameter of the segments 2 ofthe tread ring forming drum 3 is shrank.

Next, while the tread ring W and the carcass ply 50 are united andinflated by the green tire building drum 4, RRO of the green tire ismeasured by the means 15 for measuring deviation, and the measured valueis inputted into the operation means 17.

The operation means 17 compares and operates the value measured by themeans 16 for measuring holding pressure and the value measured by themeans 15 for measuring deviation, and decides a holding pressure of thesegments 7 of the transfer 1 in the next manufacturing process. That isto say, RRO of the green tire is improved by changing the holdingpressure, and this improves RRO of the tire after vulcanization.

According to the operated value, the expanding and contracting amount ofthe segments 7 of the transfer 1 is changed by the controlling means 18,and each segment 7 is arranged to hold at the decided pressure.

Explaining with reference to the flow chart shown in FIG. 9, first, theholding pressure is measured, next, RRO is measured, and at this stage,an average value of RROs measured several times is calculated. Afterthat, a next holding pressure is operated from the holding pressure andthe average RRO. If the measured holding pressure coincides with thenext holding pressure, it is unnecessary to change the holding pressure,and if the measured pressure does not coincide with the next pressure,the holding pressure needs to be changed.

Next, whether the pressure was changed or not is judged, and if notchanged, the pressure should be changed, and if the pressure waschanged, whether the process is finished or not is judged, and iffinished, it is the end of the process, and if the process should becontinued, the process is repeated from measuring the holding pressure.

The holding pressure is between 1.0 kgf/cm² and 4.0 kgf/cm². The RRO isnot sufficiently improved if the holding pressure is less than 1.0kgf/cm², and if the pressure is above 4.0 kgf/cm², the green tiredeforms in some cases because an inflate internal pressure of the greentire building drum 4 is between 1.0 kgf/cm² and 2.0 kgf/cm².

As shown in FIG. 10, it is possible to arrange the correcting means 14to possess means 20 for measuring timing of each segment 7 of thetransfer 1 to release the tread ring, operation means 21 for comparingthe value of deviation measured by the means 15 for measuring deviationand the value measured by the means 20 for measuring timing andoperating the next timing of each segment 7 to release the tread ring,and controlling means 22 for controlling timing of each segment torelease the tread ring.

The means 20 for measuring timing is, for example, arranged to obtainchange in value of a pressure sensor (for example, a distortion gauge)stuck on a face of the segment 7 which face faces the tread ring anddetect the timing to release on the basis of this change. Thecontrolling means 22 operates the expansion and contraction mechanismdescribed above and expands and contracts the segment 7 on the basis ofthe timing operated by the operation means 21.

If the RRO of the green tire has a waveform (a primary waveform) asshown in FIG. 11A, the segment 7 is arranged to release at timingdelayed from the peak P of the waveform, or, as shown in FIG. 11B, thewaveform of releasing timing of the whole segments 7 is arranged tocoincide with the primary waveform of RRO of the green tire in FIG. 11A,because RRO of the tire to be manufactured is influenced by the timingof each segment 7 of the transfer 1 to release the tread ring and theRRO of the tire to be manufactured is improved by controlling the timingto release the tread ring.

Therefore, in order to manufacture a tire using this apparatus formanufacturing a tire, first, the tread ring releasing timing of thesegment 7 is measured by the means 20 for measuring timing, and themeasured value is inputted into the operation means 21.

Next, when the green tire building drum 4 unites and inflates the treadring W and the carcass ply 50, the means 15 for measuring deviationmeasures RRO of this green tire, and the measured value is inputted intothe operation means 21.

The operation means 21 compares and operates the value measured by themeans 20 for measuring timing and the value measured by the means 15 formeasuring deviation, and decides the timing of the segments 7 of thetransfer 1 to release the tread ring in the next manufacturing process.That is to say, RRO of the green tire is improved by changing thisreleasing timing, and this improves RRO of the tire after vulcanization.

According to the operated value, the controlling means 22 changes timingof the segments 7 of the transfer 1 to expand and contract, and eachsegment 7 releases the tread ring at the decided timing.

With reference to the flowchart shown in FIG. 12, first, releasingtiming is measured, next, RRO is measured, and at this stage, an averagevalue of RROs measured several times is calculated. After that, nextreleasing timing is operated from the releasing timing and the averageRRO. If the measured releasing timing coincides with the next releasingtiming, it is needless to change the releasing timing, and if themeasured timing does not coincide with the next timing, the releasingtiming needs to be changed.

Next, whether the releasing timing was changed or not is judged, and ifnot changed, the timing needs to be changed, and if changed, whether theprocess is finished or not is judged, and if finished, this is the endof the process, and if the process should be continued, the process isrepeated from measuring the releasing timing.

The segment 7 returns within a time lag of 3 seconds because RRO doesnot change and loss of time is increased if the time lag is above 3seconds.

The correcting means 14 can be provided with, as shown in FIG. 13,operation means 26 and controlling means 27, wherein the operation means26 compares and operates a difference between a waveform which is inopposite phase against a waveform of a vertical deviation of the greentire and a waveform of a measured vertical deviation of the segment andthe controlling means 27 controls contraction and expansion in a radialdirection of the segment 2 of the tread ring forming drum 3 and arrangesthe waveform of the vertical deviation of the segment to be in oppositephase of the waveform of the vertical deviation of the green tire.

The measuring means 25 for tread ring measures a distance from an axis(a center) to the segment 2, and comprises a displacement sensor such asa laser displacement meter or a differential transformer. Further more,the controlling means 27 operates the above mentioned expansion andcontraction mechanism and expand and contract the segment 2 on the basisof the waveform phase operated by the operation means 26.

When the waveform (the primary waveform) of RRO of the green tire is thewaveform shown in FIG. 14A, the waveform of RRO of the tread ring isarranged to be the waveform shown in FIG. 14B, or, data of RRO of thegreen tire is analyzed upon occasion in order to form the tire under anappropriate condition.

A tire is manufactured using this apparatus for manufacturing a tire asfollows. The measuring means 25 for tread ring measures RRO of the treadring of the segments 2 of the tread ring forming drum 3, and themeasured value is inputted into the operation means 26. Next, this treadring W is taken out by the transfer 1 and is sent to the green tirebuilding drum 4.

Then, when the green tire building drum 4 unites and inflates the treadring W and the carcass ply 50, the means 15 for measuring deviation forgreen tire measures RRO of this green tire, and the measured value isinputted into the operation means 26.

The operation means 26 compares and operates a difference between awaveform which is in opposite phase against a waveform of a verticaldeviation of a green tire and a waveform of a vertical deviation of thesegment on the basis of the value measured by the measuring means 25 fortread ring and the value measured by the means 15 for measuringdeviation for green tire, and according to the operated value, thecontrolling means 27 changes expanding and contracting amount of thesegments 2 of the tread ring forming drum 3. That is to say, RRO of thegreen tire is improved by changing the waveform into opposite phase, andthis improves RRO of the tire after vulcanization. At this stage, it isnecessary to control the whole circumferential length of the segments 2to be constant while the tread ring is formed.

With reference to the flowchart shown in FIG. 15, first, RRO of thesegments 2 of the tread ring forming drum 3 is measured, RRO of thegreen tire is measured, and at this stage, an average value of RROs ofthe green tire measured several times is calculated. After that, awaveform of the RRO of the segments 2 is turned into opposite phase of awaveform of RRO of the green tire on the basis of the RRO of thesegments 2 and the average RRO of the green tire. If the waveform of theRRO of the segments 2 is turned into opposite phase, it is needless tochange the phase, and if not, the phase needs to be changed.

Next, whether the phase was changed or not is judged, and if notchanged, the phase needs to be changed, and if changed, whether theprocess is finished or not is judged, and if finished, this is the endof the process, and if the process should be continued, the process isrepeated from measuring RRO of the segment.

It is possible to control the green tire to be formed under anappropriate condition by measuring a waveform of RRO of the green tireon the green tire building drum 4 immediately after the green tire isformed and controlling the segments 2 of the tread ring forming drum 3to be in opposite phase of this average waveform, or, by analyzing dataof the RRO of the segments 2 and the RRO of the green tire uponoccasion.

The segments 2 of the tread ring forming drum 3 move within a range of 3mm because a protrusion of the green tire turns into a depression andthe RRO deteriorates if the range is above 3 mm.

The correcting means 14 can be provided with, as shown in FIG. 16, means35 for measuring pressure of the stitcher wheel 31, operation means 36for comparing the value measured by the means 15 for measuring deviationand the value measured by the means 35 for measuring pressure anddeciding the next pressure, and means 37 for controlling pressure of thestitcher wheel on the basis of the value operated by the operation means36. The means 35 for measuring pressure comprises, for example, an airpressure gauge.

When the waveform (the primary waveform) of RRO of the green tire is thewaveform shown in FIG. 17A, the pressure of the stitcher wheel isarranged to be the waveform shown in FIG. 17B, which coincides with theprimary waveform of RRO of the green tire shown in FIG. 17A.

A tire is manufactured using this apparatus for manufacturing a tire asfollows. The means 35 for measuring pressure measures a pressure of thestitcher wheel 31, and the measured value is inputted into the operationmeans 36. When the tread ring W and the carcass ply 50 are united andinflated, the means 15 for measuring deviation measures RRO of thisgreen tire, and the measured value is inputted into the operation means36.

The operation means 36 compares and operates the value measured by themeans 35 for measuring pressure and the value measured by the means 15for measuring deviation and decides the next pressure.

According to the operated value, the controlling means 37 changes(controls) the pressure of the stitcher wheel 31 along thecircumferential direction. The stitcher wheel presses within a rangefrom 0.3 to 3.0 kgf/cm². When the pressure is less than 0.3 kgf/cm², thestitch does not work well, and when the pressure is above 3.0 kgf/cm²,the RRO deteriorates because the tread expands and wrinkles.

With reference to the flowchart shown in FIG. 18, first, a pressure ismeasured, next, RRO is measured, and at this stage, an average value ofRROs measured several times is calculated. After that, the next pressureis operated from the pressure and the average RRO. If the measuredpressure coincides with the next pressure, it is needless to change thepressure, and if not, the pressure needs to be changed.

Next, whether the pressure was changed or not is judged, and if notchanged, the pressure needs to be changed, and if changed, whether theprocess is finished or not is judged, and if finished, this is the endof the process, and if the process should be continued, the process isrepeated from measuring the pressure.

The green tire to be formed thereby becomes a complete circle bycontrolling the pressure.

Instead of controlling the stitcher wheel pressure as described above,it is possible to stitch using a cylinder as illustrated in FIG. 7 andchange a pressure of the cylinder by controlling the position of thestitcher wheel 31.

Described below is experimental examples 1, 2, 3, and 4.

A tire manufactured by using the apparatus for manufacturing a tireshown in FIG. 1 as the experimental example 1 and a tire manufactured byusing a conventional apparatus were examined on RRO and other values,and the results are shown in Table 1.

                  TABLE 1    ______________________________________              Conventional Example                          Experimental Example 1    ______________________________________    RFV         5.42          4.18    LFV         2.88          2.51    CON         +2.10         +1.73    RRO         0.79          0.40    RRO of Green Tire                1.98          0.99    ______________________________________

A tire manufactured by using the apparatus for manufacturing a tireshown in FIG. 10 as the experimental example 2 and a tire manufacturedby using a conventional apparatus were examined on RRO and other values,and the results are shown in Table 2.

                  TABLE 2    ______________________________________              Conventional Example                          Experimental Example 2    ______________________________________    RFV         5.42          4.62    LFV         2.88          2.78    CON         +2.10         +2.02    RRO         0.79          0.61    RRO of Green Tire                1.98          1.54    ______________________________________

A tire manufactured by using the apparatus for manufacturing a tireshown in FIG. 13 as the experimental example 3 and a tire manufacturedby using a conventional apparatus were examined on RRO and other values,and the results are shown in Table 3.

                  TABLE 3    ______________________________________              Conventional Example                          Experimental Example 3    ______________________________________    RFV         6.38          5.99    LFV         2.91          2.76    CON         +1.92         +1.83    RRO         0.85          0.67    RRO of Green Tire                2.55          2.01    ______________________________________

A tire manufactured by using the apparatus for manufacturing a tireshown in FIG. 16 as the experimental example 4 and a tire manufacturedby using a conventional apparatus were examined on RRO and other values,and the results are shown in Table 4.

                  TABLE 4    ______________________________________              Conventional Example                          Experimental Example 4    ______________________________________    RFV         6.38          5.47    LFV         2.91          2.82    CON         +1.92         +0.53    RRO         0.85          0.74    RRO of Green Tire                2.55          2.18    ______________________________________

In Tables 1, 2, 3, and 4, RFV (Radial Force Variation) is a component ina direction of a load, LFV (Lateral Force Variation) is a componentperpendicular to a rotating face, and CON (Conicity) is a horizontalforce which is applied regardless of a direction of rotation.

The size of the tires is 205/65R15, and 100 samples were made, and theuniformity examination method prescribed by JASO was used in eachmeasurement.

Uniformity data of the present invention is obviously improved incomparison with the conventional method.

Therefore, the present invention provides a tire of good uniformity withaccuracy. Changing the holding pressure improves RRO of the green tire,and this improves RRO of the tire after vulcanization. Changing thereleasing timing improves RRO of the green tire, and this improves RROof the tire after vulcanization. Turning the waveform into oppositephase improves RRO of the green tire, and this improves RRO of the tireafter vulcanization. Changing pressure of the stitcher wheel 31 improvesRRO of the green tire, and this improves RRO of the tire aftervulcanization.

While preferred embodiments of the present invention have been describedin this specification, it is to be understood that the invention isillustrative and not restrictive, because various changes are possiblewithin the spirit and indispensable features.

What is claimed is:
 1. A method of manufacturing a tire in which atransfer having segments arranged along circumferential direction andreciprocated in a radial direction sends a tread ring, held by thesegments of the transfer, to a green tire building drum and said greentire building drum unites said tread ring and a carcass ply to form agreen tire, wherein the improvement comprises:after measuring a verticaldeviation of said green tire from circularity at said green tirebuilding drum while the green tire is clamped by said green tirebuilding drum, a tire to be manufactured is shaped into a completecircle by adjusting a holding pressure of each segment of said transferto compensate for the measured deviation.
 2. A method of manufacturing atire in which a tread ring is held by segments, which are arranged alonga circumferential direction and reciprocated in a radial direction, of atransfer and is sent to a green tire building drum and said green tirebuilding drum unites said tread ring and a carcass ply to form a greentire, wherein the improvement comprises:a pressure at which each segmentof said transfer holds the tread ring is measured; a vertical deviationof said green tire from circularity while the green tire is clamped bysaid green tire building drum is measured; a pressure for a tire to bemanufactured of each segment to hold a tread ring of the tire to bemanufactured is determined by comparing the measured deviation and themeasured holding pressure; and each segment holds the tread ring of thetire to be manufactured according to the determined pressure to reduceRRO of the tire to be manufactured.
 3. An apparatus for manufacturing atire provided with a green tire building drum for uniting a tread ringwith a carcass ply to form a green tire and a transfer having segmentsarranged along a circumferential direction and reciprocated in a radialdirection for holding and sending the tread ring to the green tirebuilding drum, wherein the improvement comprises:means for measuring avertical deviation of said green tire from circularity at said greentire building drum while the green tire is clamped by said green tirebuilding drum; and means for correcting a tire to be manufactured intocircularity by adjusting the holding pressure of each segment of thetransfer to compensate for the measured deviation.
 4. An apparatus formanufacturing a tire provided with a green tire building drum foruniting a tread ring and a carcass ply to form a green tire and atransfer having segments arranged along a circumferential direction andreciprocated in a radial direction for holding and sending the treadring to the green tire building drum, wherein the improvementcomprises:means for measuring a vertical deviation of said green tirefrom circularity while the green tire is clamped by said green tirebuilding drum; means for measuring a pressure at which each segment ofsaid transfer holds the tread ring; operation means for comparing thedeviation measured by the means for measuring deviation and the pressuremeasured by the means for measuring pressure and determining a pressurefor the tire to be manufactured at which each segment holds a tread ringof the tire to be manufactured according to the pressure operated by theoperation means to reduce the RRO of the tire to be manufactured.